Municipal construction codes generally require that electrical wiring, particularly in-wall wiring, be contained in fire resistant protective conduit, usually metal conduit. Where two or more electrical wires are connected the outer protective conduit must be cut or terminated in order to join the interior electrical conductors to each other. The resulting gap in protective conduit is bridged with a junction box which provides continuity of enclosure between multiple wire conduits. The ends of metal conduits are joined to the walls of the junction box while electrical wires in the conduits enter through openings in the box walls into the junction box where the wires may be interconnected with each other, e.g. with electrical nut fasteners. In the event of an electrical overload, short circuit or similar anomalous condition which causes overheating or sparking, the fire resistant junction box contains and prevents ignition of nearby flammable materials. Construction codes typically require that junction boxes meet a minimum standard of protection, e.g. two hours of protection at a given exterior temperature.
With the advent of compact light fixtures based on LED (light emitting diode) technology, it becomes possible to house small compact light fixtures directly in the junction box itself, thereby eliminating the need for the bulky and awkward sheet metal lamp housing. The relatively small junction box serves as a fire resistant enclosure for both the power supply wiring and for the light fixture itself.
In new construction, junction boxes are easily fastened to the rigid building frame, such as ceiling joists or wall studs, before drywall or other wall and ceiling material is installed. After the electrical connections are made, the wall or ceiling is then installed over the junction box, with holes cut in the ceiling or wall material for access to the boxes before being fixed into place.
In remodel construction requiring installation of junction boxes, however, it is difficult to access the building frame without removing the wall or ceiling surface first, i.e. tearing off dry wall sheet and the like. This is a labor intensive and expensive process. There is a category of junction boxes on the market specifically made for remodel construction that do not require the removal of wall and ceiling to install. These require a hole to be cut in the existing wall or ceiling surface, electrical connections to be made, and then the junction box is installed through the hole from the outside. These junction boxes have a mechanism for attaching the box to the ceiling surface, e.g. to the dry wall sheet covering, instead of to the building frame.
These remodel junction boxes typically require either an irregularly shaped hole to be cut, a clamping tab to be manually set into position before installation, a fastener to be applied to the fragile wall surface, or a combination of the these. Many of these products are designed for a single installation, damaging both the wall and the junction box if removed.
A continuing need exists for an improved wall clamping junction box.